Wireless receiving apparatus



Jan 6, 1931.

P. K. KINGDON 1,788,025

WIRELESS macmvim APPARATUS Filed April 21. 1927 i is Em ,30 laug RTTORNEYS Patented Jan. 6, 1931 PAUL KENT KINGDON, or snrswnrsmnuoxmmni new zmiLAnn T ,wranmss ancmvnla nirnnatus Application filed April 21, 1927, Serial No. 185,

This invention relates to wireless receiving apparatus and has for its object the provision of improved means for trapping the waves and cutting out or minimizing the eflect of oscillations from nearby high power broadcasting stations or the like without appreciable reduction of signal strength from stations it is desired to receive.

At present persons having wireless sets in cities or other places where there are high power broadcasting stations in the vicinity are unable to receive distant stations satistactorily owing to the influence of the local broadcasting station and therefore in many cases the sets are practically limited to receive only such local station while it is on the air.

What are known in the art as wave traps have been devised to eliminate this difiiculty but with the types of such traps at present in use the elimination of the oscillations from the local broadcasting stations unfortunately considerably reduces the signal strength of the stations it is desired to receive. The present invention has been devised to permit the oscillations of the local station being ade-' quately eliminated or minimized'while at the same time permitting the signals from the other stations with which it is desired to get in touch coming through strongly and with no appreciable diminution.

According to my invention I provide in-.

be either readtercepting means which may sets or 1n ily attachable to existing wireless corporated in fresh sets and which comprises a primary and a secondary coil, onecoil in conjunction with suitable stud switches or the like and a variable condenser to' vary the inductance of the coil being adapted to trap the-waves of the broadcasting or otherstation it is desired to'eliminate while the other coil permits the signals from the desired station to be maintained in substantially their original volume and to be tuned in on the set in the ordinary way.

The accompanying drawing illustrates the arrangement of the invention as connected to a usual type of wireless receiving set wherein a primary coil 1 is provided having tappings preferably in two groups 2 and 3 leading to as may be desired ing an input terminal,

suitable stud -switehes being minal condenser 8 also to the 453, and in New zealand January 20, 1927. y;

midi), the former connected by wire 6 direct to the ter- 7 and the latter in series with a variable terminal 7 by wire 9.

The aerial 10 is connected to the terminal .superimposed thereove 11 of the primary coil 1 the latter having r a secondary coil 12 which is connected in series with a fixed condenser 13 by wire 14 to the terminal 7.

In practice it has been found convenient for the primary coil to have 128 turns of 26 S. W. G. doublesilkcovered wire with tapv pings taken from the 80th turn onwards. The secondary coil has 80 turns of 28 S. W. G. double silk covered copper wire and is of smaller diameter wire to increase the. inductive influence of the primary and to prevent any undue decrease in the volume of the received signals.

The secondary coil is tightly wound over the input end of the primary but insulated from same by a suitable thin insulating medium.

The terminal? is connected by wire 15 to the usual aerial terminal 16 of the wireless 7 receiving set 17 which is provided with the usual earth connection 18 and adjustment dials 19.

In operation placed by the operator the dials 19 of the set 17 are to the position which he has learned by experience to be the setting for receiving the distant station, but of course the oscillations of the nearby high power broadcasting station prevent the distant station from being heard although the setting is correct for receiving same,

condenser 8 and stud therefore then adjusted so as to the variable switches 41 and 5 are vary the inductance of the primary coil 1 to suit and trap the wave length of the nearby high power station, the secondary coil 12 permitting the signals of the station or stations of wave length other than that of the station trapped and eliminated to be received and maintained at volume.

I claim:

substantially their original The combination with a radio receiver havprimary coil interpose and an aerial wire, of: a

d between said aerial wire and terminal, said primary being electrically connected with the aerial wire and including two groups of tappings a pair of stud switches one for each of sai groups 5 adapted selectively to engage the tappings thereof, one of said stud switches being in electrical connection with said input ter minal, a variable condenser j'cdnnectfed i-in series with the other of "said an switches 10 and with said terminal, a secondary"'coil--in------ inductive relation with said-primary gdlyangi electrically connected with the input terminal of the receiver, andafixedjcondenselrij' in series with said secondary coil and input 15, terminal V. If? i' In testimony whereof I affix my signature. 

